Bio-dimming lighting system

ABSTRACT

Lighting control systems are disclosed that have a plurality of current sensors and a microprocessor. A first current sensor in the plurality of current sensors measures a first current of a first LED channel, and a second current sensor measures a second current of a second LED channel. The microprocessor is configured to set a setpoint that defines a maximum current for a dimming profile of a lighting fixture, and control a biological light ratio according to the dimming profile. The ratio may be an M/P ratio of melanopic lux to photopic lux or an OPN5/OPN4 ratio of OPN5 lux to melanopic lux. The dimming profile correlates the ratio to a percentage of the maximum current.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/257,970, filed on Jan. 25, 2019 and entitled “Bio-Dimming LightingSystem,” which is hereby incorporated by reference in its entirety.

BACKGROUND

Light emitting diode (LED) technology is a maturing technology thatcontinues to show improvements in efficiency, customability and costreduction. LED technology is rapidly being deployed in a host ofindustries and markets including general lighting for homes, offices,and transportation, solid state display lighting such as in LCDs,aviation, agricultural, medical, and other fields of application. Theincreased energy efficiency of LED technology compared with otherlighting solutions coupled with the reduction of costs of LED themselvesare increasing the number of LED applications and rates of adoptionacross industries. While LED technology promises greater reliability,longer lifetimes and greater efficiencies than other lightingtechnologies, the ability to mix and independently drive different colorLEDs to produce customized and dynamic light output makes LED technologyand solid-state lighting (SSL) in general robust platforms to meet thedemands of a variety of market needs and opens the door to many newapplications of these lighting technologies.

Melanopsin is a type of photopigment belonging to a larger family oflight-sensitive retinal proteins called opsins and is found inintrinsically photosensitive retinal ganglion cells (ipRGCs) of humansand other mammals. Melanopsin plays an important non-image-forming rolein the photoentrainment of circadian rhythms as well as potentially manyother physiologic functions. Stimulation of melanopsin-containing ipRGCscontributes to various reflexive responses of the brain and body to thepresence of light. Melanopsin photoreceptors are sensitive to a range ofwavelengths and reach peak light absorption at wavelengths around480-500 (or 490) nanometers (nm). Melanopic light, that is lightcorresponding to the melanopsin action spectrum, including particularlythe wavelengths in the 480-500 nm region, is important for non-visualstimuli including physiological and neurological effects such aspupillary light reflex and circadian entrainment and/or disruption.Time-coordinated exposure, including over-exposure and under-exposure tomelanopic light, can be used to entrain and facilitate healthy circadianrhythms in humans and other mammals.

Circadian related photoreceptors are in the macular and peripheralvision regions of the retina. Melanopsin related photoreceptors are mostsensitive in the lower hemisphere of the retina. Selective stimulationof these photoreceptors is possible by directing illumination, andspecifically melanopic light, towards or away from the region of theretina where melanopic photoreceptors are most concentrated or mostsensitive or responsive. If the desire is to optimally stimulate thesephotoreceptors, then a light source that directs biological light (i.e.,melanopic light) onto this region would be a good solution. EquivalentMelanopic Lux (EML) is a metric for measuring the biological effects oflight on humans. EML as a metric is weighted to the ipRGCs response tolight and translates how much the spectrum of a light source stimulatesipRGCs and affects the circadian system. Melanopic ratio is the ratio ofmelanopic lux to photopic lux for a given light source.

While it is well known that exposure to light, both natural andartificial, can affect an individual's circadian rhythms, studies alsoindicate that the natural light of the sky during twilight, that is theshort period around dawn or dusk when the sun is near the horizon, mayhave a significant impact on circadian drive and/or the gating of sleeppressure. Although the sky appears deep blue during twilight, it hassignificantly less radiant energy in the melanopic region (e.g., 490 nm)and significantly higher radiant energy in the 420 nm region, ascompared to the sky during midday.

Scientific data indicates that the suprachiasmatic nucleus containscolor representation of the sensed color of light. During the vastmajority of the daytime, when the sun is up, the color temperature ofthe sky is between 5500 K and 7000 K. The only time when this changes isduring twilight periods when the sun is low. Common perception suggeststhat at these times the sky gets redder. However, this is not the case,and while the sun appears redder as its irradiance travels through moreof our earth's atmosphere, in fact the sky gets much bluer (e.g., attwilight, the color temperature of the sky may be at 8000-9000 K).

There are two unique and compelling circadian phenomena which coincidewith the time when the sky gets bluer. First, sleep inertia, which isthe tendency for humans to remain asleep, occurs during sleep. Uponwakening, a circadian-driven surge in blood cortisol levels helpsindividuals to wake up refreshed by mitigating sleep inertia. Thiscortisol response has been shown to synergistically occur with presenceof light. On the other end of the day, e.g., at sunset, the wakemaintenance zone portion of the circadian cycle has been demonstrated asa point of hyperactivity and enhanced neurobiological activity. It ishypothesized that this heightened activity may be an evolutionarysurvival response to ensure that individuals have sufficient alertnessand energy to complete any tasks and find safety prior to the onset ofdarkness. At the time of day around twilight (or equivalent point in acircadian photoperiod) the human neurophysiology may be affected byspecific light cues (that occur only at twilight) with regard to thebody's circadian rhythm. For example, one effect may be the initiationof a sleep gating process or conversely the absence or reduction of suchgating without exposure to the twilight.

The ability to control the circadian spectra and color temperatures oflight during dimming of LED fixtures, such as in response to anenvironmental cue or to human preference, has been implemented in somesystems. For example, systems have been disclosed in which a user cancontrol the amount of circadian stimulation depending on the time of dayor based on certain activities such as working late or jet-lag. Existingsystems often include individual controllers to adjust the colortemperature of the light and overall brightness such as through dimmers.Systems also have included learning modes to understand a user's habitsduring the day or to learn behavior according to certain activity cues.

SUMMARY

In some embodiments, a lighting control system includes a plurality ofcurrent sensors and a microprocessor. The plurality of current sensorsincludes a first current sensor and a second current sensor. The firstcurrent sensor measures a first current of a first LED channel, thesecond current sensor measures a second current of a second LED channel,and a sum of currents through the plurality of current sensors is atotal current. The microprocessor is configured to store a plurality ofsmallest average values of the total current, each of the smallestaverage values being calculated from measurements taken by the pluralityof current sensors over a plurality of sampling periods; set a setpointbased on a largest of the plurality of smallest average values, whereinthe setpoint defines a maximum current for a dimming profile of alighting fixture; and control a melanopic to photopic ratio (M/P ratio)according to the dimming profile. The dimming profile correlates the M/Pratio to a percentage of the maximum current, and the M/P ratio is aratio of a melanopic lux to a photopic lux. A maximum M/P ratio isoutput by the lighting fixture when the total current is equal to orgreater than the setpoint.

In some embodiments, a lighting control system includes a plurality ofcurrent sensors and a microprocessor. The plurality of current sensorsincludes a first current sensor and a second current sensor. The firstcurrent sensor measures a first current of a first LED channel and thesecond current sensor measures a second current of a second LED channel,wherein a sum of currents through the plurality of current sensors is atotal current. The microprocessor is configured to set a setpoint basedon a plurality of average values of the total current, wherein thesetpoint defines a maximum current for a dimming profile of a lightingfixture; and control an OPN5/OPN4 ratio according to the dimmingprofile. The dimming profile correlates the OPN5/OPN4 ratio to apercentage of the maximum current, and the OPN5/OPN4 ratio is a ratio ofan OPN5 lux to a melanopic lux. A minimum OPN5/OPN4 ratio is output bythe lighting fixture when the total current is equal to or greater thanthe setpoint.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a lighting control system, inaccordance with some embodiments.

FIG. 2 shows a dimmer control and an associated dimming profile, inaccordance with some embodiments.

FIG. 3A is a graph of spectrum containing biological light, inaccordance with some embodiments.

FIG. 3B is a graph of melanopic and photopic weighting functions forcalculating a melanopic to photopic ratio, in accordance with someembodiments.

FIGS. 4A-4D are graphs representing dimming profiles as a function ofinput current, in accordance with some embodiments.

FIG. 5 is a graph illustrating operation of a machine learningalgorithm, in accordance with some embodiments.

FIG. 6 is a flowchart of a machine learning algorithm, in accordancewith some embodiments.

FIG. 7 is a schematic of a bio-dimming electrical circuit, in accordancewith some embodiments.

FIG. 8 shows a graph of a biological lighting spectrum and dimmingprofile, in accordance with some embodiments.

FIG. 9 shows a graph of another biological lighting spectrum and dimmingprofile, in accordance with some embodiments.

FIG. 10 shows a graph of a further biological lighting spectrum anddimming profile, in accordance with some embodiments.

FIG. 11 is a schematic of a biological lighting system with colorseparation, in accordance with some embodiments.

DETAILED DESCRIPTION

Lighting systems are disclosed that provide biological light using adimming profile and a maximum output that is tailored to a user'spreferences. The maximum output may also be referred to as a maximumsetpoint or a setpoint in this disclosure, where the setpoint definesthe highest electrical current that will be utilized by LEDs in thelighting system. The system beneficially adjusts the setpoint accordingto the user's preferences in an easy-to-use and stable manner, allowingperiodic adjustments to the light through a single dimmer controlwithout erratically changing the setpoint. The biological light is alsoimproved over conventional systems by incorporating multiple wavelengthsthat play a role in circadian entrainment and by enabling spatialdistributions that further enhance circadian response. For example, thepresent lighting systems can include biological wavelengths such as oneor more of: melanopic light (approximately 490 nm) which targets thephotoreceptor OPN4, sub-dermal stimulation light (e.g., approximately660 nm and greater than approximately 700 nm (far-red)), and violetlight (approximately 380 nm) which targets the photoreceptor OPN5 andhas been found in recent studies to play a role in circadianentrainment. The dimming profiles change the proportions of biologicallight as the light is dimmed, such as by changing a ratio of melanopiclight to photopic light and/or changing a ratio of OPN5- toOPN4-targeted light. Additionally, the lighting system decreasesbiological light without compromising the visual light output (e.g.,lumen output and/or color temperature) when the light is in a highoutput range.

Dimming Control

FIG. 1 is a schematic diagram of a lighting control system 100, inaccordance with some embodiments. Lighting control system 100 includes adimmer control 110 that interacts with a microprocessor 120 to controlthe amount of light that is output by a lighting fixture 130. Dimmercontrol 110 is adjusted by a user and is shown as a slider interface inthis embodiment but may be configured in other forms such as, but notlimited to, a rotating knob, a pivoting lever or a touch screen, wherethe touch screen may have any user interface design. The dimmer control110 may provide continuously adjustable positions or may have steppedincrements. Lighting fixture 130 is shown as a multi-directional fixturein this embodiment, having both direct pendant 130 a and indirectpendant 130 b to provide downlighting and uplighting, respectively. Inother embodiments the lighting fixture 130 may be configured to provideonly direct or only indirect lighting, and can take any form (e.g.,coves, recessed, sconces, pendants). The lighting fixture 130 includesmultiple LED modules (not shown) to deliver white light and variouswavelengths having biological significance, as shall be described inmore detail later in this disclosure. In some embodiments, lightingsystem 100 can also include a controller 140 in communication with themicroprocessor 120, where the controller 140 may be a local computerhardware processor or a cloud-based processing system. The controller140 may serve as a building automation system and may be used tocompute, process, and/or store data from the lighting fixture such asmeasurements of electrical current in the LEDs, rates of changes, timepoints at which changes occur, and duration of dimming adjustments.Thus, functions described as being performed by the microprocessor inthis disclosure may by performed by the controller as well. In otherembodiments, the computation, processing, and storing of data may all beperformed locally by the microprocessor 120.

FIG. 2 is an illustration demonstrating that the dimmer control 110integrates the adjustability of overall light levels as well as abiological dimming profile of the lighting system 100 into a singlecontrol. The lighting system uniquely marries psychology (i.e., userpreferences) with biological benefits to deliver an overall dimmingprofile that provides brighter days and darker nights, as in the naturalcycle of sunlight. In the embodiment of a spectral distribution graph115 shown in FIG. 2, the system delivers a high amount of light in thepeak melanopsin sensitivity range during the day and reduces themelanopic light at night. For example, a user may use a high dimmersetting, such as setting 112 of dimmer control 110, to deliver thespectral distribution 116 of graph 115. The spectral distribution 116contains a high amount of melanopic light as indicated by the peak atapproximately 490 nm indicated by point 117. Moving the dimmer control110 to a lower setting 114 causes the spectral distribution 118 to bedelivered, where the amount of melanopic light is greatly reduced topoint 119. At the same time, the dimmer control 110 enables a user toadjust the maximum overall light output of the lighting system. Thesystem learns the highest level of light that is comfortable for theuser by monitoring the lighting levels and durations that are utilizedby the user. For example, if a user frequently maintains the dimmer at asetting 113 that is less than the highest setting 112, the lightingsystem will define a setpoint with a maximum current corresponding tosetting 113. Thus, the present lighting systems and methods beneficiallyprovide dual functions in a single dimming interface—allowing a user todim levels of biological light as well as automatically adapting to auser's preferences of maximum light levels.

FIG. 3A shows a graph 300 representing an example embodiment of aspectrum containing biological light that may be delivered in thelighting systems of the present disclosure. In FIG. 3A, the y-axis iswatts, and the x-axis is the wavelength in nanometers. The graph 300shows a total spectral output 310 (i.e., spectral power distribution)that is a combination of traditional white light spectrum 330 andbiological light 320. Biological light 320 includes wavelength peaks at490 nm (curve 322) and 660 nm (curve 324) which may be emitted togetherfrom an LED module (or chip or channel) that shall be referred to inthis disclosure as a SKYBLUE® supplement. In this disclosure, therelative amount of melanopic light in the spectrum that is being outputby the lighting system shall be referred to as a melanopic to photopic(M/P) ratio. The M/P ratio is a melanopic lux per photopic lux, which isalso known as an equivalent melanopic lux (EML). Specifically, the M/Pratio in this disclosure is calculated using weighting functions such asshown in FIG. 3B, which provide weighting based on photoreceptorsensitivity. These weighting functions are normalized to have equal areaunder the curve, but are not appropriately scaled relative to oneanother in this graph. Curve 360 is a weighting function that representsmelanopsin sensitivity and is a wavelength distribution centered aroundapproximately 490 nm. Curve 370 is a weighting function that representsphotopic sensitivity and is a wavelength distribution centered aroundapproximately 555 nm. The melanopic lux “M” is calculated as the dotproduct of the total spectral output 310 and the M weighting function,curve 360, while the photopic lux “P” is calculated as the dot productof the total spectral output 310 and the P weighting function, curve370. The M/P ratio is then calculated as M divided by P. The weightingfunctions of curve 360 and curve 370 do not have equal sensitivity andare normalized such that if curve 360 and curve 370 were equal energyspectra, the M/P ratio would be 1. For example, in this embodiment, they-axis of FIG. 3B is shown in arbitrary units that have weights of 683for the photopic curve 370 (which corresponds to the number of lumensper watt at 555 nm) and 72,983 for the melanopic curve 360 (where theunits are chosen to balance the curves 360 and 370 to have an M/P ratioof 1 at equal energy spectra).

In further embodiments, the biological light is adjusted by controllinga ratio of OPN5-targeted light to OPN4-targeted light, where anOPN5/OPN4 ratio is a ratio of an OPN5 lux to a melanopic lux. Themelanopic lux is calculated as the dot product of the total spectraloutput and an M weighting function as described above, and the OPN5 luxis similarly calculated as the dot product of the total spectral outputand an OPN5 weighting function. The OPN5/OPN4 ratio is controlledaccording to the dimming profile, where the dimming profile correlatesthe OPN5/OPN4 ratio to a percentage of the maximum current. In certainembodiments, a minimum OPN5/OPN4 ratio is output when the total currentis equal to or greater than the setpoint, such that the OPN5/OPN4 ratioincreases as the current is decreased. That is, at full output thesystem delivers a low amount of OPN5, and as the system is dimmed, theproportion of the lighting system's total current that is beingdelivered to an LED channel emitting OPN5-targeted light (e.g., 370 nmto 410 nm) increases compared to proportion of the total current to anLED channel emitting OPN4-targeted light (e.g., melanopic 480 nm to 500nm).

The lighting systems of the present disclosure adjust the biologicallight, such as the M/P ratio or OPN5/OPN4 ratio, via dimming interfacessuch as dimmer control 110 of FIG. 1. The dimming systems of the presentdisclosure are agnostic of the type of dimming interface being used andcan be utilized with various types of dimmers such as, but not limitedto, 0-10V, digital addressable lighting interface (DALI), electronic lowvoltage (ELV), or digital multiplex (DMX) types. The dimming can beperformed either automatically or manually, such as automaticallyaccording to a time of day or manually as the user dims the light outputduring the course of the day. In some embodiments, the system maydefault to delivering certain biological light ratios according to thetime of day (i.e., daylight level outputs during the morning andafternoon, and gradually dimming to nighttime levels according to sunsettiming for that geographical area) while allowing a user to override thelighting level for a period of time by manually adjust the dimminglevel. For example, a user may temporarily increase the lighting levelin an office space when they are working late, which will override theM/P (or OPN5/OPN4) ratio and the lighting level that would be deliveredaccording to the time of day for the dimming profile.

The electrical current applied to an LED determines its brightness.Conventionally, luminaires or light fixtures oftentimes are configuredto be too bright at the time of installation. Thus, the user's desiredlighting level often needs to be established in the field, where adimmer is used to achieve comfortable lighting if the levels are toobright. In conventional systems where a dimmer is used to reduce theamount of biological light, if a user dims the light for preference,then the lighting system will provide a lower biological light ratiothan what was originally designed. In contrast, the present embodimentsutilize a unique machine learning algorithm to develop an understandingof the maximum lighting level—that is, a setpoint—preferred by theuser(s). The maximum lighting level is determined by measuring theelectrical current to the lighting fixture (total current to all LEDs inthe fixture) over time, from which the algorithm derives the setpoint.The electrical current corresponding to the setpoint is the maximumcurrent that will be used in the dimming profile for the lightingfixture, where the dimming profile relates the biological light ratio toa percentage of the maximum current. That is, the M/P ratio or OPN5/OPN4ratio is adjusted as the user or the system dims the light level duringthe day, where the change in ratio is scaled to the maximum currentcorresponding to the setpoint rather than by being determined by anabsolute value of electrical current as in conventional systems. Whenthe electrical current being used at a particular time is equal to orgreater than the setpoint (e.g., if the user temporarily increases thedimmer higher than the setpoint), the maximum biological light ratiowill be delivered and will not exceed the maximum prescribed biologicallight ratio of the diming profile.

In some embodiments, each percentage output (e.g., 10% of maximumcurrent, 20%, 30%, etc.) of the dimming profile has a correspondingbiological light ratio that will be delivered. If the setpoint ischanged, as manually adjusted by the user and learned by the system tobe an actual desired change, the percentage outputs will be scaled tothat new setpoint, and the corresponding biological light ratios will bedelivered at those percentage outputs of the setpoint. For instance, inone scenario using M/P ratio as an example, the lighting system may havea total rated forward current of 0.5 A and the dimming profile isdesigned to deliver a particular nighttime M/P ratio at 30% of themaximum current (i.e., at 0.15 A). If the system determines that theuser prefers 0.4 A as the maximum lighting level, then the system willdeliver the particular nighttime M/P ratio at 0.12 A which is 30% of thenew setpoint (0.4 A). The re-scaling by the system of the dimmingprofile according to the maximum light level preferred by the userenables both the biological light and the overall lighting output of thesystem to be controlled by a single dimmer control, which improvesease-of-use compared to conventional systems.

Biological light and white light may have different efficacies. Forexample, the melanopic lumens per electrical watt of the biologicallight 320 in FIG. 3A may be different from the photopic lumens perelectrical watt of the white light spectrum 330. In some embodiments,the dimming profiles of the present disclosure uniquely account forthese differences in efficacies. In one example embodiment, the photopiclumens per watt are higher in the white light than in the biologicallight. Consequently, in a dimming profile that removes the biologicallight first, the photopic lumens remains fairly constant since thebiological light is less efficient than the white light. In other words,embodiments of the present systems and methods beneficially consider theefficacies of specific light spectra such that, for example, wavelengthsof blue light (e.g., melanopic) can be dimmed first without affectingthe photopic lumens.

FIGS. 4A-4D show example dimming profiles, where FIGS. 4A-4B illustratean embodiment of a 2-channel system (e.g., one LED channel for whitelight and a second LED channel for biological light) and FIGS. 4C-4Dillustrate an embodiment of a 3-channel system (e.g., one LED channelfor white light, a second LED channel for a melanopic component and athird channel for a far-red “twilight” component of biological light).FIGS. 4A and 4C show light output as a function of input current, whileFIGS. 4B and 4D show color temperature as a function of input current.

Looking first at dimming profile 400 of FIG. 4A, the y-axis showsnormalized lumens (relative output on a scale of 0 to 1) as well as M/Pratio. The x-axis shows the percentage of the maximum electricalcurrent. In FIG. 4A, a plot of lumens (line 402), melanopic lumens (line404, M-lumens), and M/P ratio (line 406, melanopic lux per photopic lux)over the course of the dimming profile is shown. In the dimming profile400, melanopic lux per line 404 is reduced approximately linearly by thedimming interface, with a slight increase in slope when dimming below50% current. However, visual stimulus (lumens per line 402) is reducedin a piecewise manner, with the lumens remaining constant on the upperportion (input current=50% to 100%) of the dimming interface and thendecreasing linearly. Consequently, the M/P ratio per line 406 is also apiecewise function, having a linear response with a value of zero and azero slope at lower intensities of brightness and a positive slope inthe higher intensities. FIG. 4B illustrates the resulting colortemperature graph 410, showing that the color temperature is reducedfrom 3500 K to 3000 K when the input current is reduced from 100% to 50%due to the decrease in M/P ratio.

The 3-channel dimming profile 420 of FIG. 4C shows a plot of lumens(line 422), melanopic lumens (line 424, M-lumens), and M/P ratio (line426, melanopic lux per photopic lux). Similar to FIG. 4A, the visualstimulus (lumens per line 422) is reduced in a piecewise manner, withthe lumens remaining constant on the upper portion of the dimminginterface (input current=50% to 100%) and then decreasing linearly. Themelanopic lux of line 424 has a similar slope as FIG. 4A when thecurrent is greater than 50% but decreases more rapidly below 50% than inFIG. 4A. The resulting M/P ratio decreases at a slower rate than in FIG.4A, but has a continuous decrease as the dimming current is reduced to0% rather than in a piecewise manner as in FIG. 4A. FIG. 4D shows acolor temperature graph 430 resulting from the dimming profile 420showing that the color temperature has a much greater drop than in FIG.4B, where the color temperature decreases from approximately 3500 K to3000 K when the input current is dimmed from 100% to 50%, and thendecreases to 1800 K at 0% current.

In other embodiments, dimming profiles other than linear may be used,such as logarithmic. In general, the reduction in M/P ratio (orOPN5/OPN4 ratio) within the dimming profiles may be implemented bychanging the proportion of the total current to the various LED channelsin the lighting fixture. For example, a proportion of the total currentto an LED channel that generates biological light in the lightingfixture may be decreased at a higher rate (e.g., twice the rate) than aproportion of the total current to an LED channel that generates whitelight in the lighting fixture, when the total current is in a highpercentage range of the setpoint (e.g., as the current is decreased from100% to 50% of the maximum current). In general, reduction in melanopiclight has less impact on light level in the high output range.Accordingly, in some embodiments the dimming profile uniquely utilizesthis property by producing light in which the melanopic contribution canbe reduced without a significant impact on the overall light (e.g.,brightness and/or color temperature) in the high output range (e.g.,over 50% of the maximum electrical current setpoint).

FIG. 5 is a graph 500 of LED current as a function of time,demonstrating aspects of a machine learning algorithm in accordance withsome embodiments. The LED current of the y-axis represents the totalcurrent to all the LED modules in the lighting fixture, as adjusted bythe user. The algorithm learns the user's light level preferences andmonitors electrical currents to the LEDs continuously over time,delivering the proper biological light—where M/P ratio will be used inthis example—based on the time of day or by the light level manually setby the user. Zone A of FIG. 5 represents the electrical current flowingthrough the LED panel at a particular time (starting at time=0 forillustration purposes), where the value may be determined by the initialstart-up of the system, or an existing setpoint (the maximum currentpreviously established by the system), or as adjusted by the user. Ifthe current in zone A is at or above the setpoint (e.g., manuallyincreased by the user), the maximum M/P ratio of the dimming profile isdelivered. In the scenario of FIG. 5, the current in zone A shall beassumed to be the existing setpoint. In zone B, the M/P ratio is reducedbecause the user has adjusted the current to be lower than the setpoint.The M/P ratio is gradually changed to the new state, where the new stateapplies an M/P value according the dimming profile that correlates theM/P ratio with the percentage output (i.e. the percentage that theelectrical current is of the setpoint). The change in M/P ratio followsthe dimming profile and may take place, for example, over severalminutes, such as 1, 2 or 5 minutes (note the illustrated slope betweenzones A and B is not necessarily to scale).

To determine when the setpoint should be changed in response to a user'sbehavior, the machine learning uniquely uses algorithms that react morequickly to higher setpoints (the user “dimming up” up the light level)than lower setpoints (“dimming down”). This approach for adaptivelylearning the setpoint prevents erratic changes in setpoints and is basedon a use-model in which users are more likely to dim down the lightlevel during normal usage than increasing the light level. Thus,increases that are input by the user through the dimming control areviewed as being more likely to be intentional changes than occurrencesof dimming down. To monitor dimming levels, the microprocessor measuresthe LED current over time and regularly records an average current forsampling periods that are a relatively short duration (e.g. 10-20minutes). Then at regular intervals—the intervals being longer than thesampling periods such as bi-hourly as represented by zone C—the systemsaves the smallest value of the recorded sampling period averages fromthe interval in a buffer. Saving the smallest (minimum) values that wereaveraged in each sampling period serves to filter out periodicshort-duration increases (i.e., dimming up) so that they do notinfluence the normal setpoint. The device maintains a buffer of thebi-hourly minimums over a sliding window, such as over the last 24 to 28hours, or over the last 26 hours.

Zone D demonstrates an example effect of saving the smallest averagesfrom the intervals. In zone D, the user has adjusted the current to ahigher level for a short time. In the 2-hour interval “D1” between hours13 to 15, the averages for each sampling period (e.g., every 15-20minutes) are represented by an “X.” In accordance with some embodiments,the value at D2 will be saved as the smallest average value for theinterval D1, and the peak values in zone D will be discarded. Note thatthe M/P ratio delivered during the temporary increase in zone D will bethe maximum ratio available in the dimming profile. The maximum M/Pratio cannot be exceeded even when the current is increased beyond thesetpoint (i.e., the level of zone A).

From the saved minimum averages, the largest value in a sliding window(e.g. 24- to 26-hour sliding window) is pulled from the buffer andcompared to the existing setpoint. That is, each time a new averagevalue (e.g. a bi-hourly minimum average) is saved, the system looks backat the sliding window. The buffer may be, for example, afirst-in-first-out (FIFO) buffer such that the system looksretroactively at the most recent usage trends for broad scope maximafrom the local minima that were saved. This approach of using longperiod monitoring of the high values serves to filter out routinedimming since dimming down is part of the expected use model. In otherwords, in some embodiments longer period dim-down durations aretolerated and take longer to force a downward adjustment on thesetpoint. When the largest average is found to be different from theexisting setpoint, the setpoint will be updated to the new value. Forexample, if the largest average in the sliding window is higher than theexisting setpoint, then the setpoint will be increased to the new value.Conversely, if the largest average in the sliding window is lower thanthe existing setpoint, then the setpoint will be decreased to the newvalue.

Importantly, the system requires the new value to be maintained for acertain time period before establishing a new setpoint, which results ina stable system that is not erratic but still is responsive to changesby the user. For example, having some amount of wait time beforeincreasing the setpoint prevents transient activities such as cleaningcrew activities or maintenance work from falsely affecting the setpoint.In some embodiments, the waiting time interval required for establishinga lower setpoint is longer than for establishing a higher setpoint. Inother words, the microprocessor may be configured to set the setpoint bydecreasing the setpoint when the largest of the plurality of smallestaverage values over a first time interval is less than an existingsetpoint, and increasing the setpoint when the largest of the pluralityof smallest average values over a second time interval is greater thanan existing setpoint, where the second time interval is less than thefirst time interval. In some embodiments, for example, the first timeinterval required for a decreasing the setpoint may be 4 to 26 hours,such as 6 hours or 12 hours or 24 hours, while the second time intervalrequired for increasing the setpoint may be 1 to 4 hours, such as 2hours. When a new setpoint is determined, the system may implement thenew setpoint instantaneously or may implement the new setpointgradually, such as 5-15% of the total change per second, such as 10% persecond.

In zone E the system is off, such as when a user is asleep or aworkplace is closed. During this time, the buffer data and setpoint aresaved, such as in a non-volatile memory of the microprocessor, so thatthe machine learning can resume with the previous historical data whenpower is restarted. The measuring of electrical currents and recordingof smallest averages are discontinued when the system is off.Consequently, when the system is turned on at zone F, the M/P ratio tothe LEDs is delivered at the already-established setpoint.

FIG. 6 is a flowchart 600 depicting details of the machine learningalgorithm of the microprocessor, in accordance with some embodiments.Terminology used in the flowchart 600 is listed below, along withexample values of one embodiment:

-   -   CS=Current setpoint (level having the maximum biological light        contribution)    -   AM=Average current measurement (e.g., 32 samples at 16 kHz)    -   LAM=Long period average current measurement (e.g., 32 samples of        AM)    -   LMEAS=Local (windowed) current (e.g., 1024 samples of LAM        accumulated every second, represents average current over 1024        second period)    -   LMAX=Largest LMEAS value in sliding window interval    -   SWI=Sliding window interval. LMAX values are saved at this rate        (e.g., may consist of odd hours, such as 1-25 hours, resulting        in 13 data points)    -   SWA=Sliding window current array. This is the array of LMAX        points that will be tested at the SWI to determine if a CS        adjustment is required.    -   UP_SLOPE=Rate (time value, e.g., seconds) that the CS will be        adjusted to new higher LAM setpoint (e.g., 180 seconds)    -   DOWN_SLOPE=Rate (time value, e.g., seconds) that the CS will be        adjusted to new lower LAM setpoint (e.g., 180 seconds)    -   dl/dt=Incremental change to CS when a change is required,        represented as a change in magnitude/adjustment slope.    -   LLS=Last LMAX saved. This flag indicates an LMAX is saved to        SWA, which is used to force the next LMEAS to LMAX to establish        the next high value in the array (otherwise LMAX would        perpetuate).    -   ADJUST_UP=Process flag indicating CS is gradually being        increased as a result of a learned adaptation.    -   ADJUST_DOWN=Process flag indicating CS is gradually being        decreased as a result of a learned adaptation.

The flow starting at step 610 is a function that is called every second,involving auto-sampling of electrical current measurements at afrequency that is preferably greater than the frequency used for theelectrical current drivers of the system. For example, in the embodimentof FIG. 6, samples may be taken at 16 kHz. In some embodiments, thetotal current measurement is made by taking a single measurement of thecurrent to the overall LED panel of a lighting fixture. In otherembodiments, the total current measurement is made by takingmeasurements of individual LED channels and adding them together toderive the total current that will be used in subsequent calculations.Average values (“LMEAS”) are calculated from the measurements of thetotal current over a sampling period, such as a period of 10 to 20minutes, such as 17 minutes (1024 seconds) in the embodiment shown. Aplurality of smallest average values is calculated from the measurementsof the total current over a plurality of sampling periods. In theembodiment shown, each smallest average of the total current in asliding window period is calculated by comparing LMEAS to a largestvalue (LMAX) in the sliding window period at step 612 and updating LMAXif LMEAS is less than LMAX. The sliding window interval may be, forexample two hours (bi-hourly).

The flow 620 of FIG. 6 is a process that is performed for the slidingwindow interval, such as bi-hourly (e.g., on odd number hours per step622) in the embodiment shown. The flow 620 sets a setpoint (“CS”) basedon the highest value of LMAX of the plurality of smallest averagevalues, where the setpoint defines a maximum current to be used by thedimming profile (and at which the maximum biological light will bedelivered). If the highest value of LMAX is greater than the setpoint atstep 624, the CS is adjusted upward in step 626. If the highest value ofLMAX is less than the setpoint at step 624, the CS is adjusted downwardin step 628. The microprocessor then controls the M/P ratio according tothe dimming profile, where the dimming profile correlates the M/P ratioto a percentage of the maximum current. For example, for a lightingfixture that has a first LED channel that emits a first spectrumcomprising white light and a second LED channel that emits a secondspectrum comprising biologically-tailored light (e.g., including 480-500nm and 650-670 nm), the M/P ratio represents the relative amount ofmelanopic light being output. The microprocessor instructs the LEDmodules to output the maximum M/P ratio when the total current is equalto or greater than the setpoint.

In some embodiments, an open-loop neural network may be utilized tofurther refine the adaptation of lighting level setpoints. Variousmeasurables that influence the adaptive response may be tracked, each ofwhich are assigned a weight. The weights are combined with themeasurables to calculated weighted factors. A computation of theweighted factors, such as by summing the weighted factors, may be usedto affect the learning behavior of the system. Examples of measurablesinclude, but are not limited to: elapsed time that the dimmer settinghas been steady, elapsed time that the lighting fixture has beenpowered, total run time, setting (setpoint) at initial power-up, numberof dimming adjustments that have been made since the power was turnedon, number of dimming adjustments that have been made in the lightingfixture history, rates at which the user increases or decreases thedimming control, and magnitudes at which the user increases or decreasesthe dimming control. These measurables can be used to change, forexample, how the wait-time intervals and the slopes at which newincreased or decreased setpoints are implemented. For example, themeasurables can be used to distinguish human-implemented ormachine-implemented values of measured current. In another example, themeasurables may be used to account for different fade rates capabilitiesof different lighting fixtures.

FIG. 7 is an electrical circuit schematic of an embodiment of a dimmingmodule circuit 700 that may be used in the lighting system 100 ofFIG. 1. Circuit 700 includes a current driver 710, a bio-dimmercontroller 720, and an LED engine 730. The bio-dimmer controller 720measures the electrical current going through the LED engine 730 of thelighting fixture (e.g., lighting fixture 130 of FIG. 1). Themeasurements taken by circuit 700 enable the machine learning algorithmof microprocessor 726 (i.e., the microprocessor 120 of FIG. 1) todetermine the maximum current provided to the LEDs, and consequently todetermine a setpoint at which a maximum melanopic to photopic ratio isapplied to the spectrum. The setpoint establishes the scale for the M/Pdimming profile, where the setpoint is the maximum value of the scale.

LED engine 730 includes a first LED channel 735 a, a second LED channel735 b and optionally a third LED channel 735 c. First LED channel 735 amay be, for example, a white light LED. Second and third LED channels735 b and 735 c, respectively, may generate wavelengths corresponding tobiological light such as OPN4 photoreceptor (melanopic), sub-dermaland/or OPN5 photoreceptor wavelengths which shall be described in moredetail later in this disclosure. Bio-dimmer controller 720 includes avoltage regulator 722, circuitry 724 that performs driver voltagemeasurement and pulse-width modulation (PWM) edge detection,microprocessor 726, a first current sensor 728 a, a second currentsensor 728 b and an optional third current sensor 728 c. The currentsensors 728 a, 728 b and 728 c measure the currents of LED channels 735a, 735 b and 735 c, respectively, via connector 740 and provide thecurrent measurements to microprocessor 726. In embodiments where thethird LED channel 735 c is present, the connector 740 may be a 4-pinconnection. In embodiments where the third LED channel 735 c is notpresent (i.e., the LED system is a 2-channel configuration), theconnector 740 may be a 3-pin connection.

The hardware of circuit 700 incorporates real-time current measurementas the basis for the machine learning algorithm—adapting to theoccupant's light level preferences by manipulating the balance of thebiological (e.g., SKYBLUE) and white LED sources based on the electricalcurrent and the electrical current history. Although in some embodimentsthe total current through all LED channels may be measured as a singlequantity, in the embodiment illustrated in the circuit 700, theelectrical current is measured in each LED channel separately. A benefitof measuring individual channels is identifying the current distribution(sharing) between the parallel white and biological light channels andcompensating for them so that a predictable M/P ratio is provided.Current sharing is unbalanced when there is a difference in the forwardvoltage (V_(f)) characteristic of the channels. The forward voltage ofan LED is variable, being subject to, for example, manufacturingvariability, forward current (I_(f)), temperature, aging, and wavelength(band gap energy). LED current increases in a somewhat exponentialfashion with increasing forward voltage, so small differences in thevoltage characteristics of parallel LEDs creates substantial differencesin current flow between them. In the present embodiments, a design thatmonitors current flow in the channels separately (e.g., I_(B)=SKYBLUE,I_(W)=white) as a function of the switched channel (SKYBLUE) duty cyclecan calculate ‘Normalized’ I_(B) as:

${I_{B}({Norm})} = \frac{I_{B}}{{PWM}\mspace{14mu}{Duty}\mspace{14mu}{Cycle}}$And the current ratio between the channels as:

${Current}\mspace{14mu}{Ratio}{= \frac{I_{B}({Norm})}{I_{W} + I_{B}}}$The current ratio can be used to tune the duty cycle such that apredictable current distribution (and thus M/P lumens) can be deliveredindependent of voltage variations of the diodes. Note that the currentmeasurements described above may also be used to adjust current ratiosof OPN5- and OPN4-targeted biological light.

Various embodiments of the dimmer learning of FIGS. 5-7 are possible. Insome embodiments, the lighting systems have a single dimmer control thatenables a user to adjust a total current to the lighting fixture. Amicroprocessor is configured to take measurements of a first currentthrough a first LED channel (e.g., emitting a first spectrum comprisingwhite light) and a second current through a second LED channel (e.g.,emitting a second spectrum biological lighting having wavelength peaksfrom 650 nm to 670 nm and from 480 nm to 500 nm), where a sum of thefirst current and the second current is the total current. Themicroprocessor is also configured to store a plurality of smallestaverage values of the total current, set a setpoint based on a largestof the plurality of smallest average values and control a melanopic tophotopic ratio (M/P ratio) according to a dimming profile. Each of thesmallest average values is calculated from the measurements of currentover a plurality of sampling periods. The setpoint defines a maximumcurrent for the dimming profile of the lighting fixture. The dimmingprofile correlates the M/P ratio to a percentage of the maximum current,where the M/P ratio is a ratio of a melanopic lux to a photopic lux. Amaximum M/P ratio is output when the total current being used in thelighting fixture is equal to or greater than the setpoint.

In some embodiments, the M/P ratio is changed by adjusting a firstproportion of the total current to the first LED channel and a secondproportion of the total current to the second LED channel. In someembodiments, the microprocessor is configured to set the setpoint bydecreasing the setpoint when the largest of the plurality of smallestaverage values over a first time interval is less than an existingsetpoint and increasing the setpoint when the largest of the pluralityof smallest average values over a second time interval is greater thanan existing setpoint, where the second time interval is less than thefirst time interval. For example, the first time interval may be from 24to 26 hours and the second interval from 1 to 4 hours. In someembodiments, a second proportion of the total current to the second LEDchannel is decreased at a higher rate than a first proportion of thetotal current to the first LED channel when the total current is between50% to 100% of the setpoint. For example, the second proportion may bedecreased at twice the rate as the first proportion. In someembodiments, the plurality of smallest average values and the setpointare saved in a non-volatile memory.

In some embodiments, a lighting fixture includes a first LED channelthat emits a first spectrum comprising white light, a second LED channelthat emits a second spectrum comprising biologically-tailored lighthaving wavelength peaks from 650 nm to 670 nm and from 480 nm to 500 nm,and a third LED channel that emits a third spectrum having a wavelengthpeak from 370 nm to 410 nm. A single dimmer control enables a user toadjust a total current to the lighting fixture. A microprocessor of alighting control system is configured to take measurements of current,set a setpoint based on a plurality of average values of the totalcurrent, and control an OPN5/OPN4 ratio (ratio of an OPN5 lux to amelanopic lux) according to a dimming profile. Current measurements aretaken by measuring a first current through the first LED channel, asecond current through the second LED channel and a third currentthrough the third LED channel, where a sum of the first current and thesecond current and the third current is the total current. The setpointdefines a maximum current for a dimming profile of the lighting fixture.In some embodiments, the microprocessor is configured to store theplurality of average values, each of the average values being a smallestaverage value over a sampling period; and set the setpoint based on alargest of the plurality of average values over a time interval. In someembodiments, the microprocessor is configured to set the setpoint bydecreasing the setpoint when the plurality of average values over afirst time interval is lower than an existing setpoint, and increasingthe setpoint when the plurality of average values of the total currentover a second time interval is greater than the existing setpoint, wherethe second time interval is less than the first time interval. Thedimming profile correlates the OPN5/OPN4 ratio to a percentage of themaximum current. A minimum OPN5/OPN4 ratio is output when the totalcurrent is equal to or greater than the setpoint.

Biological Light

The lighting systems of the present embodiments may use variousbiological spectral distributions depending on the application such asan office space or home environment, or daytime-only use versus day andnight use. In some embodiments, spatial considerations are alsoincorporated into the dimming profiles, in which color separation ofdifferent spectra can be implemented for fixtures with uplighting and/ordownlighting.

The lighting systems of the present embodiments utilize biological lightthat includes multiple wavelengths having biological significance. Thesuprachiasmatic nuclei in the hypothalamus regulate circadian rhythmsusing input from ganglion cells in the retina. The ganglion cellscontain proteins called opsins, where melanopsin (OPN4) responds to thewavelength of 490 nm. Illumination profiles of the present embodimentsinclude this melanopsin spectral component relevant to optical input.

Furthermore, in a recent study by Ota, et al., “Impaired CircadianPhotoentrainment in OPN4-Null Mice,” iScience, p. 299-305, Aug. 31,2018, it was found that OPN5, which has peak absorption at 380 nm, alsoplays a role in photoentrainment. In some embodiments, the lightingspectra may also uniquely include a peak wavelength at around 380 nm.Because some plastics—such as polycarbonate and poly(methylmethacrylate) that are commonly used for light fixtures—attenuate lightbelow 400 nm, some embodiments that target OPN5 may utilize wavelengthsup to 410 nm. For example, the embodiments of biological spectra includewavelength peaks from 480 nm to 500 nm and/or from 370 nm to 410 nm,where these peaks are present when the lighting output is at its maximumlevel of the dimming profile. That is, the biologically significantwavelengths are present at the maximum current of the dimming profile.The biologically significant wavelengths may decrease or increase as thecurrent is reduced, according to the specific dimming profile.

In the eye, the interaction between rods, cones and melanopsin isnuanced. Under bright light (daytime) conditions, melanopsin plays alarge role in circadian regulation, receiving some minor inputs fromcones. Thus, melanopic lux is the proper metric for daytime use. Underlow light (nighttime) conditions, melanopsin impact is limited and conesbecome a large contributor to circadian regulation, with contributionsfrom rods. Thus, it is believed that photopic lux is the proper metricfor nighttime use. Additionally, spatial distribution of light plays asignificant role in the impact of light on the eye's photoreceptors.That is, light coming from above the horizon (and being received in adownward direction by the eye) has a much stronger impact onmelanopsin-related photoreceptors than light coming from below thehorizon (being received in an upward direction). In some embodiments,the lighting systems of the present disclosure beneficially target andoptimize biological effects using lighting via spatial distributionand/or spatial modulation of illumination systems (which may also bereferred to as color separation in this disclosure), such as by creatinglayers of light that illuminate different surfaces at different times ofday (e.g., high vertical illumination during biological daytime, and lowvertical illumination during biological night time).

Illumination profiles also include enhanced spectral components that arerelevant to the skin's optical window and sub-dermal cellularstimulation (e.g., deep-red and/or infrared). When considering colorseparation, embodiments of the present disclosure uniquely recognizethat visual stimulus is not the only area of importance. Far-redwavelengths have deeper skin penetration allowing for secondary pathwaysto enhance the circadian signal. One mechanism that drives this responseis via the mitochondria, which contain a chromophore cytochrome Coxidase. Upon radiation of cytochrome C oxidase, ATP density increasesproviding intercellular signaling and increased daytime alertnesslevels. Additionally, these far-red wavelengths provide an increase incore body temperature, which further aids in circadian entrainment. Insome embodiments, maximum intensity spectra include additional far-redwavelengths designed to aid in providing extra daytime signals. Thefar-red wavelengths may be in the range from 630 nm to 1100 nm, such as700 nm to 800 nm, such as having a peak around 660 nm or 720 nm, Someembodiments uniquely utilize lighting spectra that include both 490 nmfor optical stimulation and 660 nm for sub-dermal cellular stimulation.For example, some embodiments include wavelength peaks from 650 nm to670 nm and/or from 480 nm to 500 nm and/or from 370 nm to 410 nm, wherethese peaks are present when the lighting output is at its maximum levelof the dimming profile. Some embodiments include wavelength peaksgreater than about 700 nm and/or wavelength peaks from 480 nm to 500 nmand/or from 370 nm to 410 nm, where these peaks are present when thelighting output is at its maximum level of the dimming profile

FIG. 8 is an embodiment of a graph 800 showing a first biologicallighting spectrum, which shall be referred to as a “bio-dimming”spectrum in this disclosure. The graph 800 represents a dimming profilein which the output levels of the spectrum changes as the input currentis decreased, such as being adjusted manually by a user or automaticallyby the lighting control system. Designed for offices or daytime-onlyspaces, this dimming profile allows the opportunity to remove melanopic(490 nm) biological potency in late night hours by reducing a highbiological output to a low biological output. The graph 800 showsrelative output on the y-axis (i.e., output normalized to a scale of 0to 1) as a function of wavelength for varying percentages of output. Forexample, 100% output curve 810 represents when the amount of current isbeing delivered at or above the setpoint, where the setpoint isdetermined by the machine learning algorithm. The subsequent curvesrepresent spectral distributions that will be delivered when the currentis at decreasing percentages of the setpoint. At full output curve 810(the maximum current of the dimming profile), the significant wavelengthpeaks represent white light combined with melanopic light in the 480 nmto 500 nm range (e.g., 490 nm) and sub-dermal stimulation light in the650 nm to 670 nm range (e.g., 660 nm), where the 660 nm peak appears asa broad peak in the range from 600 nm to 660 nm due to the combinationwith white light. The peak near 460 nm is also due to the white light.The full output curve 810 also includes higher amounts of far-redwavelengths (e.g., 660 nm and above or 720 nm and above) thanconventional white light spectra, to provide additional circadianentrainment through skin penetration.

As the spectrum of graph 800 is dimmed from full output curve 810 to lowoutput curve 820 (illustrated as 6.25% of the maximum current in thisembodiment), the biological light in the 480-500 nm range is graduallyremoved (e.g., linearly as a function of percentage of the maximumcurrent in some embodiments). The sub-dermal (deep red) components arealso removed as the dimming profile is decreased. In one embodiment thebio-dimming spectrum of graph 800 can be implemented by a 2-channel LEDdesign in which one LED chip (i.e., LED channel) generates white lightand the other LED chip generates the biological light (melanopic andsub-dermal). For example, the white light may have a correlated colortemperature (CCT) of 2700 K to 4000 K (e.g., approximately 3000 K or3500 K), and the biological light may be generated by the SKYBLUEsupplement LED as described earlier. As the total current to thelighting fixture is dimmed, the proportion of light between the twochips is adjusted to achieve the various M/P ratios shown by the curvesin FIG. 8. Other embodiments of LED channels for implementing thebio-dimming spectrum are possible, such as the 3-channel LED embodimentdescribed in relation to FIGS. 4C-4D.

The correlation between M/P ratio and percentage reduction of electricalcurrent can be different from the profiles shown in FIG. 8, such asusing linear, logarithmic, or piecewise correlations as described inrelation to FIGS. 4A-4D. In some embodiments, the dimming profilesuniquely remove biological light at a faster rate than the white lightat high output levels (e.g., 50%-100% of the setpoint) without impactingthe overall visual light. This minimal impact on visual light (e.g.,brightness, color temperature and/or color rendering index “CRI”) occursbecause the 480-500 nm wavelength range has less impact on visual lightthan white light. For example, a 50% reduction in the 480-500 nm peakmight only reduce the visual brightness (lumens) by 10%. This higherrate of removal in biological light is demonstrated in FIG. 8 by thewider spacing between the percentage output curves near the 490 nm peakcompared to the closer space of the curves in the 600 nm range, foroutputs greater than about 50%. In one embodiment, the dimming profilebeneficially creates only a 500 K shift from full output to a fullydimmed output, such as shifting from a 4000 K daytime spectrum withCRI=86, cyanosis observation index (COI)=3.0 and M/P=0.95 at full output(setpoint) to a 3500 K nighttime spectrum with CRI=83 and M/P 0.55 at afully dimmed setting.

In some embodiments, the white light in the spectra used in the dimmingprofiles include compensation for a 10-degree observer rather than a2-degree observer as in conventional systems. For example, the spectrumof light from a light emitting apparatus may be engineered (or tailored)to have desired chromaticity coordinates (e.g., in the CIE 1931 colorspace diagram using the 1964 10° Supplementary Standard Observer). Forexample, an LED can have an emission spectra with a strong peak in therange of 480 nm to 500 nm and the spectrum of the LED can be tailoredsuch that when the LED is combined with a traditional white LED (e.g.,with spectrum 330 shown in FIG. 3) the combined light appears white(e.g., has chromaticity coordinates within the ANSI 4000 K Bin in theCIE 1931 color space diagram). In some embodiments, LEDs with melanopicemission spectra are designed to have vector shifts in theirchromaticity coordinates from the CIE 1931 2-degree Standard Observer(i.e., the 2-degree observer) to the CIE 1964 10-degree StandardObserver (i.e., the 10-degree observer) in the CIE 1931 color spacediagram, in the negative X and positive Y directions. This is incontrast with traditional white light LEDs which have vector shifts whenmoving from the 2-degree to the 10-degree observers in the positive Xand negative Y directions. In some embodiments, the large shift in thechromaticity coordinates between the 2-degree to the 10-degree observersfor LEDs with melanopic emission spectra requires that the 10-degreeobserver is used when tailoring the chromaticity coordinates of theseLEDs. For example, when conventional methods using the 2-degree observerare used to tailor the chromaticity coordinates of light from an LEDwith a melanopic emission spectrum and light from a white LED, such thatthe combined light has chromaticity coordinates within a region of theCIE 1931 color space diagram that should appear white, then the combinedlight will have a color that may not appear white to a typical observer.The combined light may in fact appear slightly greenish, which iscommonly considered an undesirable color of light for a white lightsource intended for lighting applications. In some embodiments, the10-degree observer color matching functions are better predictors of theactual perceived color of an individual. When the 10-degree observer isused to tailor the chromaticity coordinates of light from the LEDcombination as described above, then the combined light may appear whiteto a typical observer and have improved visual aesthetic qualitiescompared to conventional circadian LED systems.

FIG. 9 is a graph 900 showing an embodiment of another biologicallighting spectrum that may be used in the dimming profiles of thepresent disclosure, where the spectrum of graph 900 shall be referred toas “sky-dimming” in this disclosure. This sky-dimming spectrum simulatesnatural light above the horizon, including a wavelength peak nearapproximately 380 nm that occurs at twilight. The embodiment of thesky-dimming spectral distribution shown in FIG. 9 includes white lightcombined with melanopic light in the 480 nm to 500 nm range, sub-dermalstimulation light in the ranges of 650 nm to 670 nm (e.g., 660 nm)and/or 700+ nm, and twilight (i.e., OPN-5 targeted light) in the 370 nmto 410 nm range. The peaks in the ranges of approximately 600 nm to 660nm and near 460 nm are due to the white light. The melanopic light insome embodiments has a peak wavelength between from 465 nm to 495 nm,with a full-width half maximum from 450 nm to 500 nm. In someembodiments, the sky-dimming profile can be implemented by a 3-channelconfiguration of 1) a custom chip (e.g., a cold white light spectrum ofCCT in a range from 8000 K to 20,000 K, such as about 17,000K, withpeaks in emission at 420 nm, 465 nm and 660 nm; and having a maximumpeak around 460-470 nm, such as 465 nm), 2) a melanopic LED channel(e.g., 480-500 nm), and 3) an OPN5 LED channel (e.g. 370-410 nm, or 405nm, or 380 nm). In some embodiments the melanopic LED channel mayinclude white light compensation for a 10-degree observer. In someembodiments, the sky-dimming profile can be implemented by a 2-channelconfiguration in which the melanopic LED is omitted, such as a 2-channelconfiguration of the custom chip and the OPN5 LED channel describedabove.

As can be seen in FIG. 9, the sky-dimming profile of graph 900 maintainsa peak in the twilight range (370 nm to 410 nm) throughout all dimmingprofile settings from the 100% output curve 910 down to the lowestsetting curve 920 (10% being the lowest output illustrated in thisgraph), increasing the OPN5/OPN4 ratio from a minimum value to highervalues as dimming occurs per the dimming profile. In some embodiments,the sky-dimming profile 900 may use only a portion of the curves shownin FIG. 9. For example, a full output of 100% maximum current mayimplement the curve 940 (which is the 40% level of the full graph 900),and the spectrum is adjusted from curve 940 to curve 920 as the currentis decreased.

The sky-dimming spectrum of graph 900 provides significant contributionof the twilight wavelengths at both the beginning and the end of theday. In addition, the sky-dimming profile of graph 900 presents a shiftin wavelength peaks. OPN5 with peak sensitivity near 380 nm contributesto the delineation of day versus night, providing an amplification ofsubsequent light exposure (either making brighter days or darkernights). This is important considering that people spend the majority oftheir time inside under electric lighting that is too dim to beconsidered day and too bright to be considered night. During twilight,as the sun sets, more atmosphere is between the sun the observer,leading to an increase of Raleigh scattering potential. This leads to acombined reduction in intensity and an increase in the relativeproportion of short wavelengths near the peak sensitivity of OPN5. Thus,during operation of dimming full output curve 910 toward low outputcurve 920, the sky-dimming profile of graph 900 implements a twilightsequence that increases the ratio of OPN5 wavelengths relative to otherwavelengths. This increase in the relative amount of 370 nm to 410 nm(e.g., 380 nm) wavelengths as the light is dimmed beneficially providesa more natural twilight scenario than conventional lighting systems. Infurther embodiments, the sky-dimming spectrum may be used to providespatial distributions of light. For example, the sky-dimming spectrummay be used to illuminate the ceiling (i.e., uplighting), or may be astand-alone fixture (e.g., cove), or may be used in an upward portion ofan up/down light.

FIG. 10 shows a graph 1000 showing an embodiment of a spectrum thatshall be referred to as “twilight dim” in this disclosure, that combinesthe bio-dimming spectrum of graph 800 and sky-dimming spectrum of graph900 into a single spectrum. Thus, the twilight dim spectrum of graph1000 is a dimming profile that provides varying melanopic and sub-dermalamounts as well as the 370-410 nm (e.g., 380 nm) OPN5 wavelength at theend of the day. In particular, the proportion of OPN5-targeted light isincreased as the current is reduced. That is, the dimming profilecorrelates an OPN5/OPN4 ratio to a percentage of the maximum current,where the OPN5/OPN4 ratio is a ratio of an OPN5 lux to a melanopic luxand a minimum OPN5/OPN4 ratio is output when the total current is equalto or greater than the setpoint. The twilight dim spectrum of graph 1000may be used in a single fixture as a downlight or as an uplight. At fulloutput 1010, the melanopic wavelength (480 nm to 500 nm) and sub-dermalcomponent (660 nm, which appears as a peak around 630 nm in combinationwith white light) are the significant components of the twilight dim,while at greatly dimmed levels (e.g. low output curve 1020 representing10% output in this example) the twilight wavelength (370 nm to 410 nm)becomes the dominant peak.

FIG. 11 shows an example of a biological lighting system beingimplemented with color separation, in which melanopic (e.g. 490 nm) andtwilight (e.g. 380 nm) components are spatially directional. Thelighting fixture in this example is a pendant fixture 1100 that haslighting components in both the upward direction (i.e. upward away fromthe ground) and the downward direction (i.e., downward toward theground). In one embodiment, the sky-dim profile of FIG. 9 can be usedfor the uplight 1110 and the bio-dimming profile of FIG. 8 can be usedin the downlight 1120. In another embodiment, the twilight-dimmingprofile of FIG. 10 can be used for the uplight 1110 and the bio-dimmingprofile of FIG. 8 can be used in the downlight 1120. As light levels aredimmed, the bio-dim profile in the downlight 1120 reduces the melanopicand sub-dermal components, while the sky-dim in the uplight 1110 reducesthe melanopic and sub-dermal components but maintains the twilight(OPN5) component. Thus, the twilight 380 nm effect is emanated fromabove the “horizon” to simulate natural sunlight and to more effectivelystimulate optical photoreceptors.

The present embodiments include various combinations of the biologicallighting profiles and spatial configurations described herein. In someembodiments, a lighting fixture includes a first LED channel that emitsa first spectrum comprising white light and a second LED channel thatemits a second spectrum comprising biologically-tailored light. Thebiologically-tailored light has a first wavelength peak in a range from650 nm to 670 nm and a second wavelength peak in a range from 480 nm to500 nm. In some embodiments, the first wavelength peak and the secondwavelength peak in the second spectrum (in the ranges from 650 nm to 670nm and from 480 nm to 500 nm) are present at the maximum current of thedimming profile. The lighting fixture further may further include athird LED channel that emits a third spectrum having a third wavelengthpeak in a range from 370 nm to 410 nm. In some embodiments, the firstspectrum, the second spectrum and the third spectrum (if present) areall emitted in a downward direction toward the ground. In someembodiments, the dimming profile has a fully dimmed setting in which thethird wavelength peak that is in a range from 370 nm to 410 nm is themaximum wavelength peak emitted by the lighting fixture. In someembodiments, as the total current is reduced, the dimming profileincreases a proportion of the total current that is delivered to thethird wavelength peak that is in the range from 370 to 410 nm emittedfrom the third LED channel.

In some embodiments, a lighting fixture includes a first LED channelthat emits a first spectrum comprising white light, a second LED channelthat emits a second spectrum comprising biologically-tailored lighthaving a first wavelength peak that is in a range from 650 nm to 670 nmand a second wavelength peak that is in a range from 480 nm to 500 nm,and a third LED channel that emits a third spectrum having a thirdwavelength peak that is in a range from 370 nm to 410 nm. Amicroprocessor is configured to take measurements of a first currentthrough the first LED channel, a second current through the second LEDchannel and a third current through the third LED channel, wherein a sumof the first current and the second current and the third current is thetotal current. The microprocessor is also configured to set a setpointbased on a plurality of average values of the total current, wherein thesetpoint defines a maximum current for a dimming profile of the lightingfixture. The microprocessor is also configured to control an OPN5/OPN4ratio according to the dimming profile. The dimming profile correlatesthe OPN5/OPN4 ratio to a percentage of the maximum current, where theOPN5/OPN4 ratio is a ratio of an OPN5 lux to a melanopic lux, and wherea minimum OPN5/OPN4 ratio is output when the total current is equal toor greater than the setpoint. In some embodiments, the white light has acolor correlated temperature that is in the range from 8000 K to 20,000K, or from 2700 K to 4000 K. In some embodiments, the first wavelengthpeak and the second wavelength peak (in the ranges from 650 nm to 670 nmand from 480 nm to 500 nm) of the second spectrum are present when themaximum current of the dimming profile is delivered to the lightingfixture. In some embodiments, the first spectrum, the second spectrumand the third spectrum are all emitted in a downward direction. In someembodiments, the first spectrum, the second spectrum and the thirdspectrum are all emitted in an upward direction away from the ground,where further embodiments may include a second lighting fixture thatemits light in a downward direction toward the ground, the secondlighting fixture including i) a fourth LED channel that emits a fourthspectrum comprising white light and ii) a fifth LED channel that emits afifth spectrum comprising biologically-tailored light having a fourthwavelength peak in a range from 650 nm to 670 nm and a fifth wavelengthpeak in a range from 480 nm to 500 nm. In some embodiments, the dimmingprofile implements the fully dimmed setting according to a time of day.In some embodiments, at the maximum current, a combined spectrum fromthe first spectrum, the second spectrum and the third spectrum istailored to have chromaticity coordinates within the ANSI 3000 K to 6500K Bin to an International Commission on Illumination (CIE) 196410-degree Standard Observer.

In some embodiments, a lighting control system includes a lightingfixture, a single dimmer control and a microprocessor. The lightingfixture includes a first LED channel that emits a first spectrumcomprising white light and a second LED channel that emits a secondspectrum comprising a wavelength peak in a range from 370 nm to 410 nm.The single dimmer control enables a user to adjust a total current tothe lighting fixture. The microprocessor is configured to a) takemeasurements of a first current through the first LED channel and asecond current through the second LED channel, where a sum of the firstcurrent and the second current is the total current; b) set a setpointbased on a plurality of average values of the total current, where thesetpoint defines a maximum current for a dimming profile of the lightingfixture; and c) control an OPN5/OPN4 ratio according to the dimmingprofile. The dimming profile correlates the OPN5/OPN4 ratio to apercentage of the maximum current, where the OPN5/OPN4 ratio is a ratioof an OPN5 lux to a melanopic lux, and where a minimum OPN5/OPN4 ratiois output when the total current is equal to or greater than thesetpoint. In some embodiments, a melanopic to photopic ratio (M/P ratio)is changed according to the dimming profile by adjusting a firstproportion of the total current to the first LED channel and a secondproportion of the total current to the second LED channel. In someembodiments, the microprocessor is configured to set the setpoint bydecreasing the setpoint when a largest of the plurality of averagevalues over a first time interval is less than an existing setpoint, andincreasing the setpoint when the largest of the plurality of averagevalues over a second time interval is greater than the existingsetpoint, where the second time interval is less than the first timeinterval. For example, the first time interval may be from 24 to 26hours and the second time interval may be from 1 to 4 hours. In someembodiments, the first spectrum and the second spectrum are all emittedin an upward direction away from the ground.

Reference has been made to embodiments of the disclosed invention. Eachexample has been provided by way of explanation of the presenttechnology, not as a limitation of the present technology. In fact,while the specification has been described in detail with respect tospecific embodiments of the invention, it will be appreciated that thoseskilled in the art, upon attaining an understanding of the foregoing,may readily conceive of alterations to, variations of, and equivalentsto these embodiments. For instance, features illustrated or described aspart of one embodiment may be used with another embodiment to yield astill further embodiment. Thus, it is intended that the present subjectmatter covers all such modifications and variations within the scope ofthe appended claims and their equivalents. These and other modificationsand variations to the present invention may be practiced by those ofordinary skill in the art, without departing from the scope of thepresent invention, which is more particularly set forth in the appendedclaims. Furthermore, those of ordinary skill in the art will appreciatethat the foregoing description is by way of example only, and is notintended to limit the invention.

What is claimed is:
 1. A lighting control system comprising: a pluralityof current sensors that includes a first current sensor and a secondcurrent sensor, wherein the first current sensor measures a firstcurrent of a first LED channel, the second current sensor measures asecond current of a second LED channel, and a sum of currents throughthe plurality of current sensors is a total current; and amicroprocessor configured to: store a plurality of smallest averagevalues of the total current, each of the smallest average values beingcalculated from measurements taken by the plurality of current sensorsover a plurality of sampling periods; set a setpoint based on a largestof the plurality of smallest average values, wherein the setpointdefines a maximum current for a dimming profile of a lighting fixture;and control a melanopic to photopic ratio (M/P ratio) according to thedimming profile, wherein the dimming profile correlates the M/P ratio toa percentage of the maximum current, and wherein the M/P ratio is aratio of a melanopic lux to a photopic lux; wherein a maximum M/P ratiois output by the lighting fixture when the total current is equal to orgreater than the setpoint.
 2. The lighting control system of claim 1further comprising a single dimmer control that enables a user to adjustthe total current to the lighting fixture.
 3. The lighting controlsystem of claim 1 further comprising a dimming interface thatautomatically adjusts the total current to the lighting fixture based oninput from a user.
 4. The lighting control system of claim 1 wherein thedimming profile implements a fully dimmed setting according to a time ofday.
 5. The lighting control system of claim 1 wherein: the first LEDchannel emits a first spectrum comprising white light; and the secondLED channel emits a second spectrum comprising biologically-tailoredlight having a first wavelength peak in a range from 650 nm to 670 nmand a second wavelength peak in a range from 480 nm to 500 nm.
 6. Thelighting control system of claim 1 wherein the microprocessor controlsthe M/P ratio by adjusting a first proportion of the total current tothe first LED channel and a second proportion of the total current tothe second LED channel.
 7. The lighting control system of claim 6,wherein: the total current is continuously measured in real-time; and acurrent ratio of the first LED channel or the second LED channel is afunction of the real-time total current.
 8. The lighting control systemof claim 1 wherein the microprocessor sets the setpoint by: decreasingthe setpoint when the largest of the plurality of smallest averagevalues over a first time interval is less than an existing setpoint; andincreasing the setpoint when the largest of the plurality of smallestaverage values over a second time interval is greater than the existingsetpoint; wherein the second time interval is less than the first timeinterval.
 9. The lighting control system of claim 8 wherein the firsttime interval is from 24 to 26 hours and the second time interval isfrom 1 to 4 hours.
 10. The lighting control system of claim 1 wherein asecond proportion of the total current to the second LED channel isdecreased at a higher rate than a first proportion of the total currentto the first LED channel when the total current is between 50% to 100%of the setpoint.
 11. The lighting control system of claim 10 wherein thesecond proportion is decreased at twice a rate as the first proportion.12. The lighting control system of claim 1 wherein the microprocessorfurther comprises a non-volatile memory that stores the plurality ofsmallest average values and the setpoint.
 13. A lighting control systemcomprising: a plurality of current sensors that includes a first currentsensor and a second current sensor, wherein the first current sensormeasures a first current of a first LED channel and the second currentsensor measures a second current of a second LED channel, wherein a sumof currents through the plurality of current sensors is a total current;and a microprocessor configured to: set a setpoint based on a pluralityof average values of the total current, wherein the setpoint defines amaximum current for a dimming profile of a lighting fixture; and controlan OPN5/OPN4 ratio according to the dimming profile, wherein the dimmingprofile correlates the OPN5/OPN4 ratio to a percentage of the maximumcurrent, and wherein the OPN5/OPN4 ratio is a ratio of an OPN5 lux to amelanopic lux; wherein a minimum OPN5/OPN4 ratio is output by thelighting fixture when the total current is equal to or greater than thesetpoint.
 14. The lighting control system of claim 13 further comprisinga single dimmer control that enables a user to adjust the total currentto the lighting fixture.
 15. The lighting control system of claim 13further comprising a dimming interface that automatically adjusts thetotal current to the lighting fixture based on input from a user. 16.The lighting control system of claim 13 wherein: the first LED channelemits a first spectrum comprising white light; and the second LEDchannel emits a second spectrum comprising biologically-tailored lighthaving a first wavelength peak in a range from 650 nm to 670 nm and asecond wavelength peak in a range from 480 nm to 500 nm.
 17. Thelighting control system of claim 16 further comprising a third currentsensor that measures a third current of a third LED channel, wherein thethird LED channel emits a third spectrum having a third wavelength peakin a range from 370 nm to 410 nm.
 18. The lighting control system ofclaim 13 wherein: the first LED channel emits a first spectrumcomprising white light; and the second LED channel emits a secondspectrum comprising a wavelength peak in a range from 370 nm to 410 nm.19. The lighting control system of claim 13 wherein the microprocessoris further configured to: store the plurality of average values, each ofthe average values being a smallest average value over a samplingperiod; and set the setpoint: i) based on a largest of the plurality ofaverage values over a time interval, ii) by decreasing the setpoint whenthe plurality of average values over a first time interval is lower thanan existing setpoint, and iii) by increasing the setpoint when theplurality of average values of the total current over a second timeinterval is greater than the existing setpoint; wherein the second timeinterval is less than the first time interval.
 20. The lighting controlsystem of claim 13 wherein the dimming profile implements the fullydimmed setting according to a time of day.